I don't remember which way you're supposed to turn it, but I do remember how I did it:
have the handle of the wrench horizontal, and push down on it, using your body weight. Then slip the belt off while it's loose. If this doesn't help I'll go do it to my 98 to re-teach myself, and try to help you further.
289 bored .030, Medium Cam, Port & polished heads, Weiand High rise intake manifold, Long tube headers, Holley 600 carb. Shift kit of some kind...